Air pulse switch having inherent holding period



Aug. 31, 1965 c. T. COOPER 3,204,056

AIR PULSE SWITCH HAVING INHERENT HOLDING PERIOD Filed July 25, 1963 Z Sheets-Sheet l 23 I4/ g i I9 2 IO/ FIG 2 I FIG. 253% ATTORNEY Aug. 31, 1965 c. T. cooPl-:R 3,204,056

AIR PULSE SWITCH HAVING INHERENT HOLDING PRIOD Filed July 25, 1963 2 Sheets-Sheet 2 INVENTOR.

CLIN TON T. COOPER fwfl/ ATTORNEY United States Patent O 3,264,056 AIR PULSE SWITCH HAVING INHERENT HOLDHNG PERIOD Clinton T. Cooper, 327 Melbourne Ave., Youngstown, Ohio Filed July 2S, 1963, Ser. No. 297,646 S Claims. (Cl. 20u-83) This invention relates generally to electrical signaling and/ or indicating systems, and more particularly to animproved .switch assembly for converting an air pulse generated by a detecting device into an electrical signal of predetermined character. A widely adopted use for such general apparatus is to detect and signal the ingress of a cu"- tomers automobile at a gasoline filling station, and commonly the electrical circuit established to operate an audible signal is of very short duration. Another use for such general `apparatus is in the provision of means to 4automatically open an entrance door as a person approaches in front of it and sometimes to also trigger the closing of the door after the person has passed through it and is departing therefrom. y

The :air-pulse generating means employed in the above systems may comprise simply a length of liexible and collapsible hose or a collapsible mat having a dispersed air chamber therein and operative when the weight of a pedestrians foot appears thereon to issue a pulse of air from said chamber. These air pulses, whether from a hose or a mat, are piped to impinge on a flexible diaphragm which on its other side actuates a moveable contact to establish an electrical circuit which, in turn, activates a signal, indicator, or other connected device such as a door actuator. The system must necessarily be rather sensitive and provision must be made for continuously equalizing the interna-l and external air pressures, it being understood that .ambient temperature variations and other factors can tend to increase or decrease the air pressure within the system in relation to the air pressure on the outer side of the diaphragm. This equalization has herei tofore been `accomplished by providing a bleed port somewhere in the system so that pressure increases due simply to temperature changes and :the `like are slowly bled off to prevent unwanted closure of the switch and to permit the ingress of atmospheric air if the pressure within the system slowly falls for any reason. This method, however, makes it impossible to sustain the closure of the switch for any appreciable length of time after the detector is actuated, necessitating holding relays or other equivalent circuitry in applications where the initiating circuit must be held closed for a predetermined period of time. It is accordingly the primary object of this invention to provide an air-pulse operated switch which remains sensitive and consistent in operation through continuous equalization of `air pressure within and outside the system when the pulse-generating detector is in standby condition but which is nevertheless operative for a predetermined interval after the detector is once actuated and remains actuated for a finite time period. Thus, it is possible in my invention to hold the switch closed for substantially all the time that the weight of a foot is on a mat detector or the weight of an automobile tire is on a hose tread. This makes it possible to simplify connected control apparatus and to adapt the switch to a Wider variety of such apparatus.

A further object of the invention is to increase the sensitivity and consistency of operation of air-pulse operated switches while yet enabling such switches to remain closed for a substantial interval of time `suflicient to insure the full actuation of connected control circuitry--for example, the completion of an actuating stroke of the movable core of a relay.

3,204,656 Patented Aug. 31, 1965 ICC The above and other objects of the invention will become apparent upon consideration f the following speciiication and the accompanying drawing wherein there are disclosed preferred embodiments of the invention.

In the drawing:

FIGURE 1 is a side elevation of a pulse switch constructed in accordance with the principles of my invention;

FIGURE 2 is a vertical section of the switch assembly of FIGURE 1;

FIGURE 3 is a sectional view of a modified form of the invention for accomplishing the objects thereof; and

FIGURE 4 is a further embodiment of the invention.

While the operative combination of the apparatus of my invention may assume many physical forms I preferably provide a hollow block 1lb having a flanged annular upper opening 11 to which is attached by pressing or soldering an apertured plate 12. The lower end of the block lll is formed in one side wall with an aperture 13 and a smaller aperture 14 is formed in the opposite side wall in alignment with the aperture 13.

Snugly received in the apertures 13 and 14 is an elongated shouldered iitting l having a thru-bore 16 therethrough which widens out at 17 and which is provided with internal threads 18 adjacent one end of the fitting. As shown, the opposite end portion of the iitting has a shoulder to overlie the outer surface of the side wall adjacent thel aperture 13, and this portion of the itting has an annular groove to receive a ilexible sealing O-ring 19. The adjacent end extremity of the fitting is of reduced diameter, as shown.

Suitably supported on the side wall of block concentric about the aperture 13 is a small solenoid 2t) carrying a slideable armature 2l having a centrally disposed bore extending longitudinally from its inner end to slideiably receive the end extremity of fitting which, as pointed out above, is of reduced diameter. interposed between the bottom wall of the bore in armature 21 and the adjacent end face of `the iitting 15 is a small coil spring 22 which operates to bias the armature 21 to the right when the solenoid 2d is deenergized. When the armature 21 is so positioned the inner annular tace of it is spaced slightly from the O-ring 19 so that communication is provided between the bore 16 and the space surrounding the armature. The latter is loosely received in the solenoid 20 so that the communicating passage thus provided is, in effect, open to the atmosphere.

The transition between bore sections 16 and 17 is conical, as shown, to provide a valve seat, and cooper-ating with this seat is a needle valve 23 having screw-threaded connection with the threads 18 whereby the area of communication between bore section 16 and 17 may be iinely adjusted by manipulation of the member i23 outside the block 10. An aperture 24 'in the side wall of bore section 17 provides communication between this bore section and the space within iblock 10. The threads 1S and cooperating threads on the needle valve 23 are sufficiently long and close litting that little air moves along this threaded connection in either axial direction.

At 'the lower end of the block lil is a coupling 25 by which the switch may be connected to la pulse generator such as the mat 2o shown in dotted lines in FIGURE 1. ln accordance with known art, the mat 26 may be formed with a 'tread-like upper surface below which is disposed collapsible tubes or other means providing air spaces which are interconnected and communicate with an outlet 2'7 for connection to the coupling 25. The device 26 operates to deliver a pulse of air through outlet 27 whenever any part of its upper tread is depressed as by a foot, for example. Soldered or otherwise suitably secured to the upper edge of the flange opening 11 of the member lil is a conical disc 28 to the outer periphery of which Ei is cemented a sealing ring 29. Stretched across this sealing ring and suitably cemented there-to is a diaphragm 3th formed of neoprene sheet or other suitable material, and it should be understood that upon the appearance of a pulse of increased air pressure in the block It@ the center pa'r't of this diaphragm will be raised.

Suitably secured to the top face o'i the plate IZ is a block 3l of insulation material which carries, rst, a tiexible conductive strip 32 mounting an electrical cont-act point on the upper surface of its free end and a pad therebelow for overlying the center portion of the diaphragm 3i?, a second tlexible conductive strip 33 is also carried by the block 31 and mounts on the lower surface of its inner free end the second switch cont-act. The vertical position of t-he inner free end of strip 33 and consequently the switch contact carried thereby is arranged to be adjusted by a screw 34 which passes down :through a threaded aperture in the upper wall of a cover 35 which is athxed to the plate l2 to enclose the switch assembly.

In actual practice, suitable insulated conductors 3d are connected to the conductive strips 32 .and 33 and lead out of the casing formed of the parts IZ and to the control apparatus with which the pulse switch is associated. The solenoid 2t? is connected in series with one of the conductors 36 so that the solenoid will be energized simultaneously with the closing of the switch contacts, it being assumed, of course, that in accordance Iwith usual practice the control apparatus will have suitable circuitry to energize the conductors 36 when the switch is closed.

In the operation of the apparatus described above, it will be apparent that during standby the valve formed by ming I9 will ybe open allowing equalizing air to enter and exit yfrom the block l@ at a rate determined by the setting of the needle valve 23. Thus, the air pressure on both sides of the diaphragm 36 remains equalized and any compressi-on in the system as caused by the pulse generator will immediately tend to lex the diaphragm 3@ and close the switch. However, the sensitivity may be readily adjusted by .adjusting the needle valve 23 `because when this needle valve is open minor pulsations can still be bled yoff through aperture 24 and bores 17 and I6 betore the diaphragm flexes suiiiciently to close the switch. This sensitivity adjustment may be used, for example, to prevent pelting rain to trigger oh? a door opening system. When, however, the detector or mat 2d is sufiioiently actuated to generate a compression pulse which cannot be dissipated rapidly by the bleed port the switch will be closed and simultaneously the solenoid 2@ will be energized to close ott the bleed port and hold the switch closed so long as the detector remains compressed, even if only in part. The practical etect of this is to keep the switch closed for an appreciable or linite length of time suilicient to actuate the associated control apparatus. Heretofore, pulse switches of the kind herein considered have been erratic in operation because the bleed or equalizing port remained open and if the diaphragm did flex sufficiently to close the contacts they often remain closed only momentarily and too short a time for full actuation of the associa-ted control.

In the embodiment of the invention shown in FIGURE 3 there is utilized a conventional diaphragm-operated switch designated generally by reference numeral 4i). Leading to this assembly and providing communication with the inner side of the diaphragm thereof is a conduit 41 which is -conencted rst to an air-pulse generator 42 which may be similar in all respects to the generator 26 described brietly above. Also connected to the conduit 41 is a block 43 mounting a tlexible diaphragm 44 the inner side of which communicates with the conduit 4l through a passageway 45 formed in the block 43. Overlying the outer peripheral edge portion of the diaphragm 44 but slightly spaced therefrom is an apertured cover member 46 mounted on the block 43. A needle valve 47 and a cooperating passageway 4d provides an adjust- 4- able bleed port between the passageway and the space Within the cap 46.

The bleed port provided by needle valve 47 normally permits the ingress and egress of air into the system including the mat or generator 42 and the switch assemfbly 4d to compensate for changes in ambient temperature as explained above in connection with the embodiment of FIGURES l and 2. It should be noted, however, that the parts 44 and 4d are so related that as the diaphragm 44 exp-ands outwardly by the application of a pulse ot air to the passage 4S the space within the cap 46 is sealed `off by reason of the diaphragm engaging the edges of the aperture in cap 46. Therefore, so long as the mat or generator 42 remains depressed by a footstep, for example, the increased pressure built up in cond'uict 4l will remain ixed to hold the switch 4d closed,

It should be understood that the showing in FIGURE 3 is illustrative only since the illustrated means for closing cfr the bleed port can as well be built into the generator 42 or in the switch assembly 40 wherein the switch-actuating diaphragm itself would also constitute the automatic valve for closing olf the bleed port.

In the embodiment of the invention shown in FIGURE 4 the general arrangement is similar to that shown in FIGURE 2 except that the solenoid 49 for closing the bleed port valve is housed in a recess formed in a block E@ which also forms the general support of the switch. Block Eil is provided with a passage 5i adapted to be connected to the pulse generator, and it should be noted that this passage leads to the switch-actuating diaphragm (52) and provides an inlet for the bleed port, the latter being adjusted by the needle valve 53 and being adapted to be closed by the valving ring mounted on the inner end ot the solenoid plunger 54. The structure of FlG- URE 4 thus far described operates in the same manner as does the apparatus of FIGURE 2 in that by means of suitable circuit connections, not shown, the solenoid 49 is energized simultaneously with the closing of the switch contacts to block the bleed port.

In FIGURE 4, however, I provide an additional feature to boost the quantity and pressure of the air in the system upon closing of the switch contacts thus reinforcing the closing force of the diaphragm on the electrical contacts and replacing whatever air escapes through the needle valve in the interval between the closing of the electrical contacts and blocking of the bleed port. All this is accomplished by mounting a disk 55 on the plunger 54 to bear against an annular collapsible air container 56 which is in communication with the passage 5I thorugh a connecting passage 57. Now when the solenoid 49 is energized upon closing of the switch contacts and the plunger S4 is drawn downwardly a quantity of air in the container 5d will be discharged outwardly into the passage 5l to provide the pulse reinforcement expalined above.

It should now be apparent that I have provided improved air-pulse operated switching arrangements which accomplish the objects initially set out in that while they provide for continuous standby pressure equalization on opposite sides of the actuating diaphragm and thus for a wider range of sensitivity in operation they nevertheless are capable of holding the contacts closed for an adequate length of time if contact is once established.

It should be obvious from the above that the principles of the invention may be embodied in various physical designs. Reference should therefore be had to the appended claims in determining the spirit and scope of the invention.

Having thus described my invention what I claim is:

l. In combination, a pneumatically operated switch, an air-pulse generator, means establishing communication between said switch and generator comprising a passage, a bleed port in a wall of said passage whereby the standby air pressure in said passage is continuously equalized with the atmospheric air pressure, and means to automatically close said port simultaneously with the closing of said switch.

2. Apparatus according to claim 1 further including means manually engageable from outside said passage to control the effective area of said port.

3. Apparatus according to claim 1 further characterized in that said means to close said port comprises a normally open solenoid-operated valve, and circuit means to energize said solenoid upon closing ofthe switch contact.

4. Apparatus according to claim 1 further characterized in that said switch comprises a movable contact, a diaphragm for moving said movable contact, a normally fixed Contact adapted to be engaged by said movable contact, and means to finely adjust the position of said normally fixed contact toward and away from said movable contact.

5. Apparatus according to claim 2 further characterized in that said switch comprises a movable contact, a diaphragm for moving said movable contact, a normally fixed contact adapted to be engaged by said mov-able contact, and means to finely adjust the position of said normally fixed contact .toward and away from said movable contact.

6. In a pneumatically operated switch, a hollow body member adapted to be connected to an air-pulse generator -and being closed in part by a flexible diaphragm, a normally fixed contact member and a cooperating movable contact member having driving connection with and actuated by said diaphragm and both contact members being positioned outside said body member, an elongated tubular fitting extending through opposite walls of said body member in air-tight relation therewith, said tubular member being of increased internal diameter in its portion extending through one of said opposed walls, and having internal screw threads in said portion, a needle valve screw-threadedly received in said portion having its pointed inner end received within the inner end of the smaller internal diametered portion of said fitting, an aperture in the side wall of said fitting to provide a passage between the space within said body member and the enlarged portion of the opening through said fitting, means outside said body member to effectively close off the outer end of the smaller internal diametered portion of said fitting, said means to close off comprising an axially outward facing sealing ring carried by said fitting, a solenoid carried by said body member concentrically about said fitting, an armature slideably received within said solenoid and having a centrally disposed bore in its inner end portion to provide an annular valving land for engagement with said sealing ring, and yieldably means normally biasing said armature to outer position Whereby said valving land is out of contact with said sealing ring, and a circuit interconnecting said switch contacts and said solenoid in series to energize the solenoid upon closure of the switch contacts to move said armature and said annular valving land into pressure engagement with said sealing ring.

7. A pneumatically-operated switch assembly comprising a horizontally disposed plate and an inverted cupshaped closure over said plate to provide a switch housing, a closure block mounted on said plate and carrying a superimposed spaced pair of flexible conductive strips carrying opposed switch contacts at their outer free ends, means extending through said closure to adjust the position of the free end of the uppermost of said strips, a hollow body member open at its upper end carried by said plate in depending relation thereto and mounting at its upper open end a flexible diaphragm which is positioned within said housing, the free end of the lowermost of said strips overlying said diaphragm whereby upon lexture of said diaphragm in an upward direction the switch contacts will be considered to be mutually engaged, means to connect said hollow body member to an air-pulse generator, means carried by said body member to establish an adjustable bleed port in a wall of said body member, and means to close off said port simultaneously with the closing of said switch contacts.

8. In a pneumatically-operated switch assembly, a hollow body member providing a space closed off in part by a switch actuating diaphragm and adapted to be connected to an air-pulse generator, a tubular fitting extending through opposite side walls of said member and having a flange adjacent one end thereof to overlie the outer surface of one of said side walls, said ange having an annular groove to mount a sealing ring which is exposed in an axial outward direction, a screw-threaded needle valve extending into said fitting from the other end thereof and an aperture in said fitting whereby a controlled bleed port may be established between said space and the said one of said fitting, a solenoid carried by said one side wall concentrically about said fitting, an armature slideably received in said solenoid and having a bore extending axially from the inner end thereof for slideably mounting over the adjacent end of said fitting outwardly of said sealing ring, means in the bottom of said bore to bias said armature in an outward direction, and the annular Iinner end face of said armature being adapted, upon energization of said solenoid, to be moved into pressure-sealing relation with said ring.

References Cited by the Examiner UNITED STATES PATENTS 2,251,180 7/41 Wesley et al. 200-86 3,116,382 12/63 Loomis et al. 200-86 

1. IN COMBINATION, A PNEUMATICALLY OPERATED SWITCH, AN AIR-PULSE GENERATOR, MEANS ESTABLISING COMMUNICATION BETWEEN SAID SWITCH AND GENERATOR COMPRISING A PASSAGE, A BLEED PORT IN A WALL OF SAID PASSGE WHEREBY THE STANDBY AIR PRESSURE IN SAID PASSAGE IS CONTINUOUSLY EQUALIZED 